Control circuit and method for controlling a power semiconductor switch

1. A driving circuit for driving a power semiconductor switch, comprising a signal-processing unit for generating a gate signal for a gate of the power semiconductor switch, the driving circuit including a resistor series circuit which is connectable to a power terminal, used for the current supply, of the power semiconductor switch, and whose output is connected to a first input of the signal-processing unit, and the signal-processing unit having a second input for a reference voltage for the collector-emitter voltage of the power semiconductor switch,

wherein

at least one semiconductor device is provided which is implemented in such a way that it is operated in breakdown in response to the exceedance of a specific collector-emitter voltage of the power semiconductor switch, an output of the at least one semiconductor device being connected via a conductive interconnect to a terminal between the resistors of the resistor series circuit or to the resistor-series-circuit output which is connected to the signal-processing unit, and the breakdown voltage of the at least one semiconductor device being selected in such a way that the potential at the output of the at least one semiconductor device is greater than the potential at the gate of the power semiconductor switch in the ON state of the power semiconductor switch,

wherein

a further semiconductor device is provided which is connected in series to the at least one first semiconductor device, a switch being positioned parallel to this further semiconductor device and its gate being connected indirectly or directly to an output of the signal-processing unit, to which output, in particular, the gate of the power semiconductor switch is connectable, the driving circuit being implemented in such a way that the signal-processing unit closes the switch in the ON state of the power semiconductor switch and/or at the beginning of the circuit-breaking operation of the power semiconductor switch.

2. The driving circuit as recited in claim 1 ,

wherein

the potential at the output of the at least one semiconductor device, particularly the breakdown voltage of the at least one semiconductor device, is greater than 100 V.

3. The driving circuit as recited in claim 1 ,

wherein

the at least one semiconductor device is a Zener diode, an avalanche diode and/or transient-voltage suppressor diode.

4. The driving circuit as recited in claim 1 ,

wherein

a plurality of semiconductor devices are provided, which are connected in series.

5. The driving circuit as recited in claim 4 ,

wherein

at least one further conductive interconnect is provided which connects an output of one of the further semiconductor devices to a further terminal between the resistors of the resistor series circuit.

6. The driving circuit as recited in claim 1 ,

wherein

the output of the resistor series circuit is connected via a response-time network to the first input of the signal-processing unit, the response-time network including a response-time resistor.

7. The driving circuit as recited in claim 6 ,

wherein

provided between the resistor series circuit and the response-time network and parallel to the response-time network, is a frequency-dependent and/or time-dependent impedance which, in particular, includes a series connection of a resistor and a capacitor, or the series connection of a resistor and a switch controlled by the signal-processing unit.

8. A method for driving a power semiconductor switch having a driving circuit as recited in claim 1 , the signal-processing unit ascertaining, from the signal applied to its first input and from the reference voltage for the collector-emitter voltage of the power semiconductor switch, a gate signal for the gate of the power semiconductor switch,

wherein

in response to the exceedance of a specific collector-emitter voltage, the at least one semiconductor device is operated in breakdown and the potential at that output of the resistor series circuit which is connected with the conductive interconnect, or at the terminal which is between the resistors of the resistor series circuit and is connected with the conductive interconnect, is limited to a value which is greater than the potential at gate of the power semiconductor switch in the ON state of the power semiconductor switch,

wherein

in at least one of the ON state of the power semiconductor switch and the beginning of the circuit-breaking operation of the power semiconductor switch, the voltage across a further semiconductor device, which is connected in series to the at least one semiconductor device, is reduced with the aid of a switch, positioned parallel to this further semiconductor device, when the semiconductor devices are operated in breakdown mode.

9. The method as recited in claim 8 ,

wherein

the potential at that output of the resistor series circuit which is connected with the conductive interconnect, or at the terminal which is between the resistors of the resistor series circuit and is connected with the conductive interconnect, is limited to a value which is greater than 100 V.

10. The method as recited in claim 8 ,

wherein

in response to the exceedance of the breakdown voltage of the at least one semiconductor device, the signal-processing unit increases the value of the gate signal for the gate of the power semiconductor switch.

11. The method as recited in claim 8 ,

wherein

the actuating signal for the switch positioned parallel to the further semiconductor device is formed by the gate signal for the gate of the power semiconductor switch or is derived from it or from a switching command for the signal-processing unit.